You have not arrived at his second sentence. Notice that there is no we, no be and keep is in the present tense.
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GraduateMar 17 '14 at 4:35

@Graduate: as I say in my answer his second is not correct because "need" has no subject. I rectified his second sentence in my answer.
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LaureMar 17 '14 at 6:42

@Laure Thank you so much. Let me ask you one more question about 'be'. Why are we using 'be' here (It could be done)?
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user62015Mar 20 '14 at 5:47

@user62015. "It could be done." is a sentence in the passive voice. See what I wrote in my answer "Be" is part of the passive voice (be+past participle of the verb).This page might help you understanding the passive voice.
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LaureMar 20 '14 at 6:18